It is desirous in obtaining sample cores from bore holes to know the direction that certain parts of the core bear with relation to the surface of the ground where the bore has been made. To accomplish this, complicated mechanisms have heretofore been used. An example is a mechanism including, for instance, a compass and photographic equipment. One disadvantage in such a mechanism is that the drilling operation sends vibrations through the coring equipment and drilling fluid. The vibrations tend to blur the photographs, making it necessary to completely halt the drilling and fluid pumping operations and allow the vibrations to subside, which consumes time, to obtain a clear photograph.
Further, with the use of a compass, the apparatus and the ground material must be non-magnetic so that the compass will not be affected. One such mechanism is shown in U.S. Pat. No. 3,450,216 dated Jun. 17, 1969. It is also known for core taking apparatus to include a core barrel attached to the bottom end of the drill string and isolated from the rotation by bearings. In such an arrangement, friction between the core and core barrel provides the only force holding the core barrel from rotating. Such an apparatus is shown in U.S. Pat. No. 3,004,614. If, however, the core should break, the core barrel will rotate, and all orientation will be lost. In fact, many prior core sampling apparatus rely on the integrity of the core.
It is also known to score the core with internally extending projections, such as, for example, as shown in U.S. Pat. No. 1,701,784. One disadvantage with such projections is that they have been evenly spaced around the core barrel, and thus the orientation of the core may not be accurately ascertained. A further disadvantage is that sometimes the projections fail to adequately score the core.
Another disadvantage of conventional coring device is that such devices are prone to inner rod failure due to clogging at the bottom of the coring device. Conventional coring devices, such as the coring device 100 shown in FIG. 3, are double tube core barrels, with outer tubes 110 and inner tubes 111 mounted on separate bearing assemblies. The inner and outer tubes 110, 111 do not rotate together. Through this arrangement, the amount of water contacting the core is minimized. Blockages sometimes occur during coring operations. A consequence of such blockages is that the inner orienting tubes 111 are prevented from rotating. The continued force of the motor used to rotate the inner orienting tubes 111 eventually leads to the breakage of the tubes 111, thus destroying the orientation of the core.
The invention provides a device for orienting a core cut in a bore hole. The device includes a plurality of orienting rod sections connected one to another into a rotatable orienting rod, and a core barrel attached to one end of the rotatable orienting rod. The core barrel is configured to receive the core and the core barrel includes a plurality of projections extending from an inward surface of the core barrel. At least three projections are grouped together on the inward surface opposite from a fourth projection.
The invention further provides a system for cutting a core in a bore hole. The system includes a driving means, a plurality of orienting rod sections connected together as an orienting rod, the orienting rod being rotatable by the driving means, a core barrel attached to one end of the orienting rod, and a ratchet assembly for protecting the orienting rod from breakage caused by a clog in said core barrel.
The invention also provides a method for obtaining a cut core from a bore hole. The method includes the steps of extending a rotatable orienting rod, with a core barrel attached thereto, into the bore hole, cutting the core, depositing the core in the core barrel, and scribing the core with a plurality of grouped projections and one opposing projection located on an inner surface of the core barrel.